[unreadable] [unreadable] The Prospective Investigation of Pulmonary Embolism Diagnosis III (PIOPED III) is a multicenter prospective investigation designed to determine the diagnostic accuracy of gadolinium enhanced magnetic resonance angiography of the pulmonary arteries (Gd-MRA) in combination with magnetic resonance venography of the veins of the thighs (MRV) in patients with clinically suspected acute pulmonary embolism (PE). This is the proposal for the Administrative Center, and it contains the scientific portion of PIOPED III. The diagnostic accuracy of Gd-MRA alone and in combination with MRV will be expressed as sensitivity, specificity, and likelihood ratio for positive and negative tests. The study design is a prospective study of consecutive patients incorporating standardized inclusion/exclusion criteria, complete ascertainment of patient characteristics and outcomes, uniform diagnostic criteria, and unbiased paired central readings of imaging studies. Over a period of two years, 1256 patients with suspected acute PE will be recruited at 7 clinical centers. Composite reference standards will be used to diagnose VTE and exclude PE. It is expected that 314 patients will have acute VTE and they will undergo Gd-MRA/MRV. It is expected that 942 patients will be shown not to have PE. From among this group, 314 patients will be randomly selected for the index test, Gd-MRA/MRV. The strengths of this proposal are: 1) the importance of the problem of PE in terms of lives lost from under diagnosis and major bleeding from over diagnosis, 2) the potential applicability of a new technology for the diagnosis of PE, 3) a strong investigative team that has collaborated previously in successful research in PE, 4) a protocol that parallels previously proven protocols for the evaluation of a diagnostic test for PE. [unreadable] [unreadable]